Field of the Invention
The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device, which may be driven at a low voltage and has improved luminescence lifetime.
Discussion of the Related Art
An organic light emitting display (OLED) is a self light emitting display device, and is a display device based on an organic light emitting device that injects electrons and holes from each of a cathode for electron injection and an anode for hole injection into a light emitting layer and emits light when excitons obtained by combination of the injected electrons and holes are transited from an excited state to a ground state.
The organic light emitting display may be categorized into a top emission type, a bottom emission type, and a dual emission type depending on a direction to which light is emitted, and may be categorized into a passive matrix type and an active matrix type depending on a driving mode.
The organic light emitting display may be fabricated to be lightweight and slim in size, as it does not need a separate light source such as a backlight for a liquid crystal display (LCD). Also, the organic light emitting display is favorable in view of power consumption due to low voltage driving and also is excellent for color realization, a response speed, a viewing angle, and a contrast ratio (CR), whereby the organic light emitting display has been studied as a display for next generation applications.
As a display of high resolution has been developed, the number of pixels per unit area has been increased and high luminance has been required. However, there is a limitation in luminance (Cd) of a unit area (A) in view of a luminescent structure of the organic light emitting display, and problems occur in that reliability of the organic light emitting device is deteriorated and power consumption is increased due to increase of an applied current.
Therefore, to overcome such technical limitations that deteriorate the quality and productivity of the organic light emitting device, luminescence efficiency and lifetime of the organic light emitting device need to be improved and power consumption should be reduced. In this respect, various studies for developing an organic light emitting device, which may improve luminescence efficiency, lifetime of an organic light emitting layer and viewing angle characteristics while maintaining a color area, have been made.